In recent years, as an imaging apparatus used for medical image diagnosis and non-destructive inspection using X rays, a radiation imaging apparatus utilizing a flat panel detector (hereinafter referred to as an FPD) formed of a semiconductor member has been widely used. Such a radiation imaging apparatus is used as a digital imaging apparatus which performs still-image shooting, such as general shooting, and moving-image shooting, such as fluorography, in medical image diagnosis, for example. Such an imaging apparatus is generally configured such that the FPD is synchronized with an X-ray generation apparatus. However, when the FPD is installed, the FPD is required to be connected to the X-ray generation apparatus, and therefore, an installation location of the FPD is restricted.
In PTL 1, a reading circuit periodically performs a reading operation in a state in which all switch means is in an off state before imaging of a radiation image. Then a process of converting charge leaked from radiation detection elements into leakage data and a process of resetting the radiation detection elements are alternately performed in a repetitive manner using switch means so that start of irradiation with radial rays is detected in accordance with the read leakage data.